diff mbox series

i2c: Drop legacy muxing pseudo-drivers

Message ID 20230926133725.5c3fb96e@endymion.delvare
State Superseded
Headers show
Series i2c: Drop legacy muxing pseudo-drivers | expand

Commit Message

Jean Delvare Sept. 26, 2023, 11:37 a.m. UTC
The i2c-amd756-s4882 and i2c-nforce2-s4985 muxing pseudo-drivers were
written at a time when the i2c core did not support muxing. They are
essentially board-specific hacks. If we had to add support for these
boards today, we would implement it in a completely different way.

These Tyan server boards are 18 years old by now, so I very much doubt
any of these is still running today. So let's just drop this clumsy
code. If anyone really still needs this support and complains, I'll
rewrite it in a proper way on top of i2c-mux.

This also fixes the following warnings:
drivers/i2c/busses/i2c-amd756.c:286:20: warning: symbol 'amd756_smbus' was not declared. Should it be static?
drivers/i2c/busses/i2c-nforce2.c:123:20: warning: symbol 'nforce2_smbus' was not declared. Should it be static?

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Andi Shyti <andi.shyti@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
---
 MAINTAINERS                            |    2 
 drivers/i2c/busses/Kconfig             |   26 ---
 drivers/i2c/busses/Makefile            |    2 
 drivers/i2c/busses/i2c-amd756-s4882.c  |  245 ---------------------------------
 drivers/i2c/busses/i2c-amd756.c        |    4 
 drivers/i2c/busses/i2c-nforce2-s4985.c |  240 --------------------------------
 drivers/i2c/busses/i2c-nforce2.c       |   16 --
 7 files changed, 1 insertion(+), 534 deletions(-)

Comments

Andi Shyti Sept. 26, 2023, 9:27 p.m. UTC | #1
Hi Jean,

On Tue, Sep 26, 2023 at 01:37:25PM +0200, Jean Delvare wrote:
> The i2c-amd756-s4882 and i2c-nforce2-s4985 muxing pseudo-drivers were
> written at a time when the i2c core did not support muxing. They are
> essentially board-specific hacks. If we had to add support for these
> boards today, we would implement it in a completely different way.
> 
> These Tyan server boards are 18 years old by now, so I very much doubt
> any of these is still running today. So let's just drop this clumsy
> code. If anyone really still needs this support and complains, I'll
> rewrite it in a proper way on top of i2c-mux.

do you have such devices?

I'm somewhat conflicted, on one hand I like the cleanup. But on
the other I think that they don't do any harm if they stay where
they are. There are lots of drivers that look outdated and need
maintenance, we can't just remove them... right?

Thanks,
Andi

> This also fixes the following warnings:
> drivers/i2c/busses/i2c-amd756.c:286:20: warning: symbol 'amd756_smbus' was not declared. Should it be static?
> drivers/i2c/busses/i2c-nforce2.c:123:20: warning: symbol 'nforce2_smbus' was not declared. Should it be static?
> 
> Signed-off-by: Jean Delvare <jdelvare@suse.de>
> Cc: Andi Shyti <andi.shyti@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
Jean Delvare Sept. 27, 2023, 8:24 a.m. UTC | #2
Hi Andi,

On Tue, 26 Sep 2023 23:27:20 +0200, Andi Shyti wrote:
> On Tue, Sep 26, 2023 at 01:37:25PM +0200, Jean Delvare wrote:
> > The i2c-amd756-s4882 and i2c-nforce2-s4985 muxing pseudo-drivers were
> > written at a time when the i2c core did not support muxing. They are
> > essentially board-specific hacks. If we had to add support for these
> > boards today, we would implement it in a completely different way.
> > 
> > These Tyan server boards are 18 years old by now, so I very much doubt
> > any of these is still running today. So let's just drop this clumsy
> > code. If anyone really still needs this support and complains, I'll
> > rewrite it in a proper way on top of i2c-mux.  
> 
> do you have such devices?

I don't. If I did, I would have written proper muxing code for them
long ago.

> I'm somewhat conflicted, on one hand I like the cleanup. But on
> the other I think that they don't do any harm if they stay where
> they are.

Every piece of code which lives in the kernel tree has a maintenance
cost. As a matter of fact, these 2 "drivers" were affected by 6
tree-wide or subsystem-wide changes over the last 14 years. No actual
driver-specific change was applied during that period of time.

Currently these "drivers" also cause build-time warnings (with W=1),
which Nick understandably wanted to clear, and this is even the reason
why I looked into that and wrote this removal patch.

> There are lots of drivers that look outdated and need
> maintenance, we can't just remove them... right?

Actually we can, and should, if we suspect there are no users left.
There's absolutely no reason to spend time maintaining and building old
drivers which have no users left. Unused drivers also take disk space
and network bandwidth world-wide, and represent an additional attack
surface from a security perspective.
Wolfram Sang Sept. 27, 2023, 7:44 p.m. UTC | #3
On Tue, Sep 26, 2023 at 01:37:25PM +0200, Jean Delvare wrote:
> The i2c-amd756-s4882 and i2c-nforce2-s4985 muxing pseudo-drivers were
> written at a time when the i2c core did not support muxing. They are
> essentially board-specific hacks. If we had to add support for these
> boards today, we would implement it in a completely different way.
> 
> These Tyan server boards are 18 years old by now, so I very much doubt
> any of these is still running today. So let's just drop this clumsy
> code. If anyone really still needs this support and complains, I'll
> rewrite it in a proper way on top of i2c-mux.
> 
> This also fixes the following warnings:
> drivers/i2c/busses/i2c-amd756.c:286:20: warning: symbol 'amd756_smbus' was not declared. Should it be static?
> drivers/i2c/busses/i2c-nforce2.c:123:20: warning: symbol 'nforce2_smbus' was not declared. Should it be static?
> 
> Signed-off-by: Jean Delvare <jdelvare@suse.de>

What is this based on? Doesn't apply to 6.6-rc3 here?
Jean Delvare Sept. 27, 2023, 8:21 p.m. UTC | #4
On Wed, 27 Sep 2023 21:44:30 +0200, Wolfram Sang wrote:
> On Tue, Sep 26, 2023 at 01:37:25PM +0200, Jean Delvare wrote:
> > The i2c-amd756-s4882 and i2c-nforce2-s4985 muxing pseudo-drivers were
> > written at a time when the i2c core did not support muxing. They are
> > essentially board-specific hacks. If we had to add support for these
> > boards today, we would implement it in a completely different way.
> > 
> > These Tyan server boards are 18 years old by now, so I very much doubt
> > any of these is still running today. So let's just drop this clumsy
> > code. If anyone really still needs this support and complains, I'll
> > rewrite it in a proper way on top of i2c-mux.
> > 
> > This also fixes the following warnings:
> > drivers/i2c/busses/i2c-amd756.c:286:20: warning: symbol 'amd756_smbus' was not declared. Should it be static?
> > drivers/i2c/busses/i2c-nforce2.c:123:20: warning: symbol 'nforce2_smbus' was not declared. Should it be static?
> > 
> > Signed-off-by: Jean Delvare <jdelvare@suse.de>  
> 
> What is this based on? Doesn't apply to 6.6-rc3 here?

6.5.5. I'll rebase on top of 6.6-rc3 tomorrow, sorry.
diff mbox series

Patch

--- linux-6.5.orig/MAINTAINERS
+++ linux-6.5/MAINTAINERS
@@ -9779,12 +9779,10 @@  F:	Documentation/i2c/busses/i2c-viapro.r
 F:	drivers/i2c/busses/i2c-ali1535.c
 F:	drivers/i2c/busses/i2c-ali1563.c
 F:	drivers/i2c/busses/i2c-ali15x3.c
-F:	drivers/i2c/busses/i2c-amd756-s4882.c
 F:	drivers/i2c/busses/i2c-amd756.c
 F:	drivers/i2c/busses/i2c-amd8111.c
 F:	drivers/i2c/busses/i2c-i801.c
 F:	drivers/i2c/busses/i2c-isch.c
-F:	drivers/i2c/busses/i2c-nforce2-s4985.c
 F:	drivers/i2c/busses/i2c-nforce2.c
 F:	drivers/i2c/busses/i2c-piix4.c
 F:	drivers/i2c/busses/i2c-sis5595.c
--- linux-6.5.orig/drivers/i2c/busses/Kconfig
+++ linux-6.5/drivers/i2c/busses/Kconfig
@@ -62,19 +62,6 @@  config I2C_AMD756
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-amd756.
 
-config I2C_AMD756_S4882
-	tristate "SMBus multiplexing on the Tyan S4882"
-	depends on I2C_AMD756 && X86
-	help
-	  Enabling this option will add specific SMBus support for the Tyan
-	  S4882 motherboard.  On this 4-CPU board, the SMBus is multiplexed
-	  over 8 different channels, where the various memory module EEPROMs
-	  and temperature sensors live.  Saying yes here will give you access
-	  to these in addition to the trunk.
-
-	  This driver can also be built as a module.  If so, the module
-	  will be called i2c-amd756-s4882.
-
 config I2C_AMD8111
 	tristate "AMD 8111"
 	depends on PCI
@@ -248,19 +235,6 @@  config I2C_NFORCE2
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-nforce2.
 
-config I2C_NFORCE2_S4985
-	tristate "SMBus multiplexing on the Tyan S4985"
-	depends on I2C_NFORCE2 && X86
-	help
-	  Enabling this option will add specific SMBus support for the Tyan
-	  S4985 motherboard.  On this 4-CPU board, the SMBus is multiplexed
-	  over 4 different channels, where the various memory module EEPROMs
-	  live.  Saying yes here will give you access to these in addition
-	  to the trunk.
-
-	  This driver can also be built as a module.  If so, the module
-	  will be called i2c-nforce2-s4985.
-
 config I2C_NVIDIA_GPU
 	tristate "NVIDIA GPU I2C controller"
 	depends on PCI
--- linux-6.5.orig/drivers/i2c/busses/Makefile
+++ linux-6.5/drivers/i2c/busses/Makefile
@@ -14,7 +14,6 @@  obj-$(CONFIG_I2C_ALI1535)	+= i2c-ali1535
 obj-$(CONFIG_I2C_ALI1563)	+= i2c-ali1563.o
 obj-$(CONFIG_I2C_ALI15X3)	+= i2c-ali15x3.o
 obj-$(CONFIG_I2C_AMD756)	+= i2c-amd756.o
-obj-$(CONFIG_I2C_AMD756_S4882)	+= i2c-amd756-s4882.o
 obj-$(CONFIG_I2C_AMD8111)	+= i2c-amd8111.o
 obj-$(CONFIG_I2C_CHT_WC)	+= i2c-cht-wc.o
 obj-$(CONFIG_I2C_I801)		+= i2c-i801.o
@@ -22,7 +21,6 @@  obj-$(CONFIG_I2C_ISCH)		+= i2c-isch.o
 obj-$(CONFIG_I2C_ISMT)		+= i2c-ismt.o
 obj-$(CONFIG_I2C_NCT6793)	+= i2c-nct6793.o
 obj-$(CONFIG_I2C_NFORCE2)	+= i2c-nforce2.o
-obj-$(CONFIG_I2C_NFORCE2_S4985)	+= i2c-nforce2-s4985.o
 obj-$(CONFIG_I2C_NVIDIA_GPU)	+= i2c-nvidia-gpu.o
 obj-$(CONFIG_I2C_PIIX4)		+= i2c-piix4.o
 obj-$(CONFIG_I2C_SIS5595)	+= i2c-sis5595.o
--- linux-6.5.orig/drivers/i2c/busses/i2c-amd756-s4882.c
+++ /dev/null
@@ -1,245 +0,0 @@ 
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * i2c-amd756-s4882.c - i2c-amd756 extras for the Tyan S4882 motherboard
- *
- * Copyright (C) 2004, 2008 Jean Delvare <jdelvare@suse.de>
- */
- 
-/*
- * We select the channels by sending commands to the Philips
- * PCA9556 chip at I2C address 0x18. The main adapter is used for
- * the non-multiplexed part of the bus, and 4 virtual adapters
- * are defined for the multiplexed addresses: 0x50-0x53 (memory
- * module EEPROM) located on channels 1-4, and 0x4c (LM63)
- * located on multiplexed channels 0 and 5-7. We define one
- * virtual adapter per CPU, which corresponds to two multiplexed
- * channels:
- *   CPU0: virtual adapter 1, channels 1 and 0
- *   CPU1: virtual adapter 2, channels 2 and 5
- *   CPU2: virtual adapter 3, channels 3 and 6
- *   CPU3: virtual adapter 4, channels 4 and 7
- */
-
-#include <linux/module.h>
-#include <linux/kernel.h>
-#include <linux/slab.h>
-#include <linux/init.h>
-#include <linux/i2c.h>
-#include <linux/mutex.h>
-
-extern struct i2c_adapter amd756_smbus;
-
-static struct i2c_adapter *s4882_adapter;
-static struct i2c_algorithm *s4882_algo;
-
-/* Wrapper access functions for multiplexed SMBus */
-static DEFINE_MUTEX(amd756_lock);
-
-static s32 amd756_access_virt0(struct i2c_adapter * adap, u16 addr,
-			       unsigned short flags, char read_write,
-			       u8 command, int size,
-			       union i2c_smbus_data * data)
-{
-	int error;
-
-	/* We exclude the multiplexed addresses */
-	if (addr == 0x4c || (addr & 0xfc) == 0x50 || (addr & 0xfc) == 0x30
-	 || addr == 0x18)
-		return -ENXIO;
-
-	mutex_lock(&amd756_lock);
-
-	error = amd756_smbus.algo->smbus_xfer(adap, addr, flags, read_write,
-					      command, size, data);
-
-	mutex_unlock(&amd756_lock);
-
-	return error;
-}
-
-/* We remember the last used channels combination so as to only switch
-   channels when it is really needed. This greatly reduces the SMBus
-   overhead, but also assumes that nobody will be writing to the PCA9556
-   in our back. */
-static u8 last_channels;
-
-static inline s32 amd756_access_channel(struct i2c_adapter * adap, u16 addr,
-					unsigned short flags, char read_write,
-					u8 command, int size,
-					union i2c_smbus_data * data,
-					u8 channels)
-{
-	int error;
-
-	/* We exclude the non-multiplexed addresses */
-	if (addr != 0x4c && (addr & 0xfc) != 0x50 && (addr & 0xfc) != 0x30)
-		return -ENXIO;
-
-	mutex_lock(&amd756_lock);
-
-	if (last_channels != channels) {
-		union i2c_smbus_data mplxdata;
-		mplxdata.byte = channels;
-
-		error = amd756_smbus.algo->smbus_xfer(adap, 0x18, 0,
-						      I2C_SMBUS_WRITE, 0x01,
-						      I2C_SMBUS_BYTE_DATA,
-						      &mplxdata);
-		if (error)
-			goto UNLOCK;
-		last_channels = channels;
-	}
-	error = amd756_smbus.algo->smbus_xfer(adap, addr, flags, read_write,
-					      command, size, data);
-
-UNLOCK:
-	mutex_unlock(&amd756_lock);
-	return error;
-}
-
-static s32 amd756_access_virt1(struct i2c_adapter * adap, u16 addr,
-			       unsigned short flags, char read_write,
-			       u8 command, int size,
-			       union i2c_smbus_data * data)
-{
-	/* CPU0: channels 1 and 0 enabled */
-	return amd756_access_channel(adap, addr, flags, read_write, command,
-				     size, data, 0x03);
-}
-
-static s32 amd756_access_virt2(struct i2c_adapter * adap, u16 addr,
-			       unsigned short flags, char read_write,
-			       u8 command, int size,
-			       union i2c_smbus_data * data)
-{
-	/* CPU1: channels 2 and 5 enabled */
-	return amd756_access_channel(adap, addr, flags, read_write, command,
-				     size, data, 0x24);
-}
-
-static s32 amd756_access_virt3(struct i2c_adapter * adap, u16 addr,
-			       unsigned short flags, char read_write,
-			       u8 command, int size,
-			       union i2c_smbus_data * data)
-{
-	/* CPU2: channels 3 and 6 enabled */
-	return amd756_access_channel(adap, addr, flags, read_write, command,
-				     size, data, 0x48);
-}
-
-static s32 amd756_access_virt4(struct i2c_adapter * adap, u16 addr,
-			       unsigned short flags, char read_write,
-			       u8 command, int size,
-			       union i2c_smbus_data * data)
-{
-	/* CPU3: channels 4 and 7 enabled */
-	return amd756_access_channel(adap, addr, flags, read_write, command,
-				     size, data, 0x90);
-}
-
-static int __init amd756_s4882_init(void)
-{
-	int i, error;
-	union i2c_smbus_data ioconfig;
-
-	if (!amd756_smbus.dev.parent)
-		return -ENODEV;
-
-	/* Configure the PCA9556 multiplexer */
-	ioconfig.byte = 0x00; /* All I/O to output mode */
-	error = i2c_smbus_xfer(&amd756_smbus, 0x18, 0, I2C_SMBUS_WRITE, 0x03,
-			       I2C_SMBUS_BYTE_DATA, &ioconfig);
-	if (error) {
-		dev_err(&amd756_smbus.dev, "PCA9556 configuration failed\n");
-		error = -EIO;
-		goto ERROR0;
-	}
-
-	/* Unregister physical bus */
-	i2c_del_adapter(&amd756_smbus);
-
-	printk(KERN_INFO "Enabling SMBus multiplexing for Tyan S4882\n");
-	/* Define the 5 virtual adapters and algorithms structures */
-	if (!(s4882_adapter = kcalloc(5, sizeof(struct i2c_adapter),
-				      GFP_KERNEL))) {
-		error = -ENOMEM;
-		goto ERROR1;
-	}
-	if (!(s4882_algo = kcalloc(5, sizeof(struct i2c_algorithm),
-				   GFP_KERNEL))) {
-		error = -ENOMEM;
-		goto ERROR2;
-	}
-
-	/* Fill in the new structures */
-	s4882_algo[0] = *(amd756_smbus.algo);
-	s4882_algo[0].smbus_xfer = amd756_access_virt0;
-	s4882_adapter[0] = amd756_smbus;
-	s4882_adapter[0].algo = s4882_algo;
-	s4882_adapter[0].dev.parent = amd756_smbus.dev.parent;
-	for (i = 1; i < 5; i++) {
-		s4882_algo[i] = *(amd756_smbus.algo);
-		s4882_adapter[i] = amd756_smbus;
-		snprintf(s4882_adapter[i].name, sizeof(s4882_adapter[i].name),
-			 "SMBus 8111 adapter (CPU%d)", i-1);
-		s4882_adapter[i].algo = s4882_algo+i;
-		s4882_adapter[i].dev.parent = amd756_smbus.dev.parent;
-	}
-	s4882_algo[1].smbus_xfer = amd756_access_virt1;
-	s4882_algo[2].smbus_xfer = amd756_access_virt2;
-	s4882_algo[3].smbus_xfer = amd756_access_virt3;
-	s4882_algo[4].smbus_xfer = amd756_access_virt4;
-
-	/* Register virtual adapters */
-	for (i = 0; i < 5; i++) {
-		error = i2c_add_adapter(s4882_adapter+i);
-		if (error) {
-			printk(KERN_ERR "i2c-amd756-s4882: "
-			       "Virtual adapter %d registration "
-			       "failed, module not inserted\n", i);
-			for (i--; i >= 0; i--)
-				i2c_del_adapter(s4882_adapter+i);
-			goto ERROR3;
-		}
-	}
-
-	return 0;
-
-ERROR3:
-	kfree(s4882_algo);
-	s4882_algo = NULL;
-ERROR2:
-	kfree(s4882_adapter);
-	s4882_adapter = NULL;
-ERROR1:
-	/* Restore physical bus */
-	i2c_add_adapter(&amd756_smbus);
-ERROR0:
-	return error;
-}
-
-static void __exit amd756_s4882_exit(void)
-{
-	if (s4882_adapter) {
-		int i;
-
-		for (i = 0; i < 5; i++)
-			i2c_del_adapter(s4882_adapter+i);
-		kfree(s4882_adapter);
-		s4882_adapter = NULL;
-	}
-	kfree(s4882_algo);
-	s4882_algo = NULL;
-
-	/* Restore physical bus */
-	if (i2c_add_adapter(&amd756_smbus))
-		printk(KERN_ERR "i2c-amd756-s4882: "
-		       "Physical bus restoration failed\n");
-}
-
-MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
-MODULE_DESCRIPTION("S4882 SMBus multiplexing");
-MODULE_LICENSE("GPL");
-
-module_init(amd756_s4882_init);
-module_exit(amd756_s4882_exit);
--- linux-6.5.orig/drivers/i2c/busses/i2c-amd756.c
+++ linux-6.5/drivers/i2c/busses/i2c-amd756.c
@@ -283,7 +283,7 @@  static const struct i2c_algorithm smbus_
 	.functionality	= amd756_func,
 };
 
-struct i2c_adapter amd756_smbus = {
+static struct i2c_adapter amd756_smbus = {
 	.owner		= THIS_MODULE,
 	.class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
 	.algo		= &smbus_algorithm,
@@ -398,5 +398,3 @@  module_pci_driver(amd756_driver);
 MODULE_AUTHOR("Merlin Hughes <merlin@merlin.org>");
 MODULE_DESCRIPTION("AMD756/766/768/8111 and nVidia nForce SMBus driver");
 MODULE_LICENSE("GPL");
-
-EXPORT_SYMBOL(amd756_smbus);
--- linux-6.5.orig/drivers/i2c/busses/i2c-nforce2-s4985.c
+++ /dev/null
@@ -1,240 +0,0 @@ 
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * i2c-nforce2-s4985.c - i2c-nforce2 extras for the Tyan S4985 motherboard
- *
- * Copyright (C) 2008 Jean Delvare <jdelvare@suse.de>
- */
-
-/*
- * We select the channels by sending commands to the Philips
- * PCA9556 chip at I2C address 0x18. The main adapter is used for
- * the non-multiplexed part of the bus, and 4 virtual adapters
- * are defined for the multiplexed addresses: 0x50-0x53 (memory
- * module EEPROM) located on channels 1-4. We define one virtual
- * adapter per CPU, which corresponds to one multiplexed channel:
- *   CPU0: virtual adapter 1, channel 1
- *   CPU1: virtual adapter 2, channel 2
- *   CPU2: virtual adapter 3, channel 3
- *   CPU3: virtual adapter 4, channel 4
- */
-
-#include <linux/module.h>
-#include <linux/kernel.h>
-#include <linux/slab.h>
-#include <linux/init.h>
-#include <linux/i2c.h>
-#include <linux/mutex.h>
-
-extern struct i2c_adapter *nforce2_smbus;
-
-static struct i2c_adapter *s4985_adapter;
-static struct i2c_algorithm *s4985_algo;
-
-/* Wrapper access functions for multiplexed SMBus */
-static DEFINE_MUTEX(nforce2_lock);
-
-static s32 nforce2_access_virt0(struct i2c_adapter *adap, u16 addr,
-				unsigned short flags, char read_write,
-				u8 command, int size,
-				union i2c_smbus_data *data)
-{
-	int error;
-
-	/* We exclude the multiplexed addresses */
-	if ((addr & 0xfc) == 0x50 || (addr & 0xfc) == 0x30
-	 || addr == 0x18)
-		return -ENXIO;
-
-	mutex_lock(&nforce2_lock);
-	error = nforce2_smbus->algo->smbus_xfer(adap, addr, flags, read_write,
-						command, size, data);
-	mutex_unlock(&nforce2_lock);
-
-	return error;
-}
-
-/* We remember the last used channels combination so as to only switch
-   channels when it is really needed. This greatly reduces the SMBus
-   overhead, but also assumes that nobody will be writing to the PCA9556
-   in our back. */
-static u8 last_channels;
-
-static inline s32 nforce2_access_channel(struct i2c_adapter *adap, u16 addr,
-					 unsigned short flags, char read_write,
-					 u8 command, int size,
-					 union i2c_smbus_data *data,
-					 u8 channels)
-{
-	int error;
-
-	/* We exclude the non-multiplexed addresses */
-	if ((addr & 0xfc) != 0x50 && (addr & 0xfc) != 0x30)
-		return -ENXIO;
-
-	mutex_lock(&nforce2_lock);
-	if (last_channels != channels) {
-		union i2c_smbus_data mplxdata;
-		mplxdata.byte = channels;
-
-		error = nforce2_smbus->algo->smbus_xfer(adap, 0x18, 0,
-							I2C_SMBUS_WRITE, 0x01,
-							I2C_SMBUS_BYTE_DATA,
-							&mplxdata);
-		if (error)
-			goto UNLOCK;
-		last_channels = channels;
-	}
-	error = nforce2_smbus->algo->smbus_xfer(adap, addr, flags, read_write,
-						command, size, data);
-
-UNLOCK:
-	mutex_unlock(&nforce2_lock);
-	return error;
-}
-
-static s32 nforce2_access_virt1(struct i2c_adapter *adap, u16 addr,
-				unsigned short flags, char read_write,
-				u8 command, int size,
-				union i2c_smbus_data *data)
-{
-	/* CPU0: channel 1 enabled */
-	return nforce2_access_channel(adap, addr, flags, read_write, command,
-				      size, data, 0x02);
-}
-
-static s32 nforce2_access_virt2(struct i2c_adapter *adap, u16 addr,
-				unsigned short flags, char read_write,
-				u8 command, int size,
-				union i2c_smbus_data *data)
-{
-	/* CPU1: channel 2 enabled */
-	return nforce2_access_channel(adap, addr, flags, read_write, command,
-				      size, data, 0x04);
-}
-
-static s32 nforce2_access_virt3(struct i2c_adapter *adap, u16 addr,
-				unsigned short flags, char read_write,
-				u8 command, int size,
-				union i2c_smbus_data *data)
-{
-	/* CPU2: channel 3 enabled */
-	return nforce2_access_channel(adap, addr, flags, read_write, command,
-				      size, data, 0x08);
-}
-
-static s32 nforce2_access_virt4(struct i2c_adapter *adap, u16 addr,
-				unsigned short flags, char read_write,
-				u8 command, int size,
-				union i2c_smbus_data *data)
-{
-	/* CPU3: channel 4 enabled */
-	return nforce2_access_channel(adap, addr, flags, read_write, command,
-				      size, data, 0x10);
-}
-
-static int __init nforce2_s4985_init(void)
-{
-	int i, error;
-	union i2c_smbus_data ioconfig;
-
-	if (!nforce2_smbus)
-		return -ENODEV;
-
-	/* Configure the PCA9556 multiplexer */
-	ioconfig.byte = 0x00; /* All I/O to output mode */
-	error = i2c_smbus_xfer(nforce2_smbus, 0x18, 0, I2C_SMBUS_WRITE, 0x03,
-			       I2C_SMBUS_BYTE_DATA, &ioconfig);
-	if (error) {
-		dev_err(&nforce2_smbus->dev, "PCA9556 configuration failed\n");
-		error = -EIO;
-		goto ERROR0;
-	}
-
-	/* Unregister physical bus */
-	i2c_del_adapter(nforce2_smbus);
-
-	printk(KERN_INFO "Enabling SMBus multiplexing for Tyan S4985\n");
-	/* Define the 5 virtual adapters and algorithms structures */
-	s4985_adapter = kcalloc(5, sizeof(struct i2c_adapter), GFP_KERNEL);
-	if (!s4985_adapter) {
-		error = -ENOMEM;
-		goto ERROR1;
-	}
-	s4985_algo = kcalloc(5, sizeof(struct i2c_algorithm), GFP_KERNEL);
-	if (!s4985_algo) {
-		error = -ENOMEM;
-		goto ERROR2;
-	}
-
-	/* Fill in the new structures */
-	s4985_algo[0] = *(nforce2_smbus->algo);
-	s4985_algo[0].smbus_xfer = nforce2_access_virt0;
-	s4985_adapter[0] = *nforce2_smbus;
-	s4985_adapter[0].algo = s4985_algo;
-	s4985_adapter[0].dev.parent = nforce2_smbus->dev.parent;
-	for (i = 1; i < 5; i++) {
-		s4985_algo[i] = *(nforce2_smbus->algo);
-		s4985_adapter[i] = *nforce2_smbus;
-		snprintf(s4985_adapter[i].name, sizeof(s4985_adapter[i].name),
-			 "SMBus nForce2 adapter (CPU%d)", i - 1);
-		s4985_adapter[i].algo = s4985_algo + i;
-		s4985_adapter[i].dev.parent = nforce2_smbus->dev.parent;
-	}
-	s4985_algo[1].smbus_xfer = nforce2_access_virt1;
-	s4985_algo[2].smbus_xfer = nforce2_access_virt2;
-	s4985_algo[3].smbus_xfer = nforce2_access_virt3;
-	s4985_algo[4].smbus_xfer = nforce2_access_virt4;
-
-	/* Register virtual adapters */
-	for (i = 0; i < 5; i++) {
-		error = i2c_add_adapter(s4985_adapter + i);
-		if (error) {
-			printk(KERN_ERR "i2c-nforce2-s4985: "
-			       "Virtual adapter %d registration "
-			       "failed, module not inserted\n", i);
-			for (i--; i >= 0; i--)
-				i2c_del_adapter(s4985_adapter + i);
-			goto ERROR3;
-		}
-	}
-
-	return 0;
-
-ERROR3:
-	kfree(s4985_algo);
-	s4985_algo = NULL;
-ERROR2:
-	kfree(s4985_adapter);
-	s4985_adapter = NULL;
-ERROR1:
-	/* Restore physical bus */
-	i2c_add_adapter(nforce2_smbus);
-ERROR0:
-	return error;
-}
-
-static void __exit nforce2_s4985_exit(void)
-{
-	if (s4985_adapter) {
-		int i;
-
-		for (i = 0; i < 5; i++)
-			i2c_del_adapter(s4985_adapter+i);
-		kfree(s4985_adapter);
-		s4985_adapter = NULL;
-	}
-	kfree(s4985_algo);
-	s4985_algo = NULL;
-
-	/* Restore physical bus */
-	if (i2c_add_adapter(nforce2_smbus))
-		printk(KERN_ERR "i2c-nforce2-s4985: "
-		       "Physical bus restoration failed\n");
-}
-
-MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
-MODULE_DESCRIPTION("S4985 SMBus multiplexing");
-MODULE_LICENSE("GPL");
-
-module_init(nforce2_s4985_init);
-module_exit(nforce2_s4985_exit);
--- linux-6.5.orig/drivers/i2c/busses/i2c-nforce2.c
+++ linux-6.5/drivers/i2c/busses/i2c-nforce2.c
@@ -117,20 +117,6 @@  static const struct dmi_system_id nforce
 
 static struct pci_driver nforce2_driver;
 
-/* For multiplexing support, we need a global reference to the 1st
-   SMBus channel */
-#if IS_ENABLED(CONFIG_I2C_NFORCE2_S4985)
-struct i2c_adapter *nforce2_smbus;
-EXPORT_SYMBOL_GPL(nforce2_smbus);
-
-static void nforce2_set_reference(struct i2c_adapter *adap)
-{
-	nforce2_smbus = adap;
-}
-#else
-static inline void nforce2_set_reference(struct i2c_adapter *adap) { }
-#endif
-
 static void nforce2_abort(struct i2c_adapter *adap)
 {
 	struct nforce2_smbus *smbus = adap->algo_data;
@@ -411,7 +397,6 @@  static int nforce2_probe(struct pci_dev
 		return -ENODEV;
 	}
 
-	nforce2_set_reference(&smbuses[0].adapter);
 	return 0;
 }
 
@@ -420,7 +405,6 @@  static void nforce2_remove(struct pci_de
 {
 	struct nforce2_smbus *smbuses = pci_get_drvdata(dev);
 
-	nforce2_set_reference(NULL);
 	if (smbuses[0].base) {
 		i2c_del_adapter(&smbuses[0].adapter);
 		release_region(smbuses[0].base, smbuses[0].size);